The present invention relates to an improved component for a plasma processing system and, more particularly, to an optical window deposition shield employed in a plasma processing system to provide optical access to a process space through a deposition shield.
The fabrication of integrated circuits (IC) in the semiconductor industry typically employs plasma to create and assist surface chemistry within a plasma reactor necessary to remove material from and deposit material to a substrate. In general, plasma is formed within the plasma reactor under vacuum conditions by heating electrons to energies sufficient to sustain ionizing collisions with a supplied process gas. Moreover, the heated electrons can have energy sufficient to sustain dissociative collisions and, therefore, a specific set of gases under predetermined conditions (e.g., chamber pressure, gas flow rate, etc.) are chosen to produce a population of charged species and chemically reactive species suitable to the particular process being performed within the chamber (e.g., etching processes where materials are removed from the substrate or deposition processes where materials are added to the substrate).
Although the formation of a population of charged species (ions, etc.) and chemically reactive species is necessary for performing the function of the plasma processing system (i.e. material etch, material deposition, etc.) at the substrate surface, other component surfaces on the interior of the processing chamber are exposed to the physically and chemically active plasma and, in time, can erode. The erosion of exposed components in the plasma processing system can lead to a gradual degradation of the plasma processing performance and ultimately to complete failure of the system.
In order to minimize the damage sustained by exposure to the processing plasma, components of the plasma processing system, known to sustain exposure to the processing plasma, are coated with a protective barrier. For example, components fabricated from aluminum can be anodized to produce a surface layer of aluminum oxide, which is more resistant to the plasma. In another example, a consumable or replaceable component, such as one fabricated from silicon, quartz, alumina, carbon, or silicon carbide, can be inserted within the processing chamber to protect the surfaces of more valuable components that would impose greater costs during frequent replacement. Furthermore, it is desirable to select surface materials that minimize the introduction of unwanted contaminants, impurities, etc. to the processing plasma and possibly to the devices formed on the substrate.
In both cases, the inevitable failure of the protective coating, either due to the integrity of the protective barrier or the integrity of the fabrication of the protective barrier, and the consumable nature of the replaceable components demands frequent maintenance of the plasma processing system. This frequent maintenance can produce costs associated with plasma processing down-time and new plasma processing chamber components, which can be excessive.
The present invention provides an improved optical window deposition shield for optical access to a process space in a plasma processing system through a deposition shield, wherein the design and fabrication of the optical window deposition shield advantageously addresses the above-identifed shortcomings.
It is an object of the present invention to provide an optical window deposition shield comprising a plug configured to extend through an opening formed in the deposition shield, a flange coupled to the plug and configured to attach the optical window deposition shield to the deposition shield. The plug comprises a frontal surface and a perimeter surface coupled thereto. The flange comprises a first surface, a second surface, and an edge surface, wherein the first surface further comprises a mating surface.
It is another object of the present invention that the optical window deposition shield comprises at least one optical through-hole coupled to the frontal surface of the plug and the second surface of the flange and configured to permit the passage of light, wherein such an optical through-hole can comprise an exposed entrant surface coupled to the frontal surface of the plug, and an interior through-hole surface coupled to the exposed entrant surface and to the second surface of the flange.
It is another object of the present invention that the optical window deposition shield comprises a plurality of fastening receptors coupled to the mating surface of the first surface of the flange and the second surface of the flange and configured to receive fastening devices, wherein each fastening receptor can comprise an entrant region, a through-hole region, an exit through-hole, an interior fastener surface, and a recessed fastener surface.
It is another object of the present invention that the optical window deposition shield further comprises a protective barrier formed on a plurality of exposed surfaces of the optical window deposition shield exposed to the processing plasma.
It is a further object of the present invention that the exposed surfaces of the deposition shield comprise the frontal surface of the plug, the perimeter surface of the plug, the first surface of the flange excluding the mating surface, and the exposed entrant surface of the at least one optical through-hole.
The present invention further provides a method of producing the optical window deposition shield in the plasma processing system comprising the steps: fabricating the optical window deposition shield; anodizing the optical window deposition shield to form a surface anodization layer on the optical window deposition shield; machining the exposed surfaces on the optical window deposition shield to remove the surface anodization layer; and forming a protective barrier on the exposed surfaces.
The present invention provides another method of producing the optical window deposition shield in the plasma processing system comprising the steps: fabricating the optical window deposition shield; masking the exposed surfaces on the optical window deposition shield to prevent formation of a surface anodization layer; anodizing the optical window deposition shield to form the surface anodization layer on the optical window deposition shield; unmasking the exposed surfaces; and forming a protective barrier on the exposed surfaces.
The present invention provides another method of producing the optical window deposition shield in the plasma processing system comprising the steps: fabricating the optical window deposition shield; and forming a protective barrier on exposed surfaces.
The present invention also includes another method that combines masking portions of the exposed surfaces before anodization and leaving other portions of the exposed surfaces unmasked; anodizing the unmasked surfaces; machining the portions of the exposed surfaces that were unmasked and which were anodized; unmasking the masked portions of the exposed surfaces; and forming a protective barrier on the exposed surfaces.
Any of the above methods may also optionally include machining anodized (or otherwise coated) surfaces that are not exposed surfaces (e.g., to obtain a bare metal connection where the machined surface will mate with another part).
It is another object of the present invention that the optical window deposition shield serves as an insert, wherein the insert comprises no optical through-holes and can be produced using any of the above methods.